Method of manufacturing foil-shaped metal grains



Nov. 24, 1931. E. KRAMER 1,832,863

METHOD OF MANUFACTURING FOIL SHAPED METAL GRAINS Filed Oct. 21. 1929 Patented Nov. 24, 1931 UNITED," STATES PATENT OFFICE minim 1 01: BERLIN, GERMANY METHOD OF MANUFACTURING FOIL-SHAPED METAL GRAINS Application med omen- 21, 1929,18eria1 Io. 401,299, and in Germany October 22, 1928. a

My invention relates to the manufacture 661331. The improvement consists in rendering it possible to carry out the method in a continuous manner, in such a way, that a part cularly uniform product is attained which is important for the quality of the product. At the same time. the. output .is increased. that is to say, not only the efficiency of the method is increased, but also the output in a certain unit of time. Another advantage of 'the present im roved method is that the apparatus in wh ch it is carried out need not be opened while the serviceis 11'.) going on so that no air can find access to the bronze: when the bronze is hot it is easily affected by air, and, therefore, at all events 'air should be excluded. It is particularly advisable to fill the apparatus with an indif-' ferent gas to thereby prevent disastrous explosions which are likely to occur, for instance. with aluminium bronze. Another adatantage attained bv the method according 6 to this invention is this that still finer foils f 1s can be prevented from oxidizing or even burning after having left the machine as is frequently the case with aluminium bronze.

M For practicing my im roved method I make use of a machine in which the spreading of the metal powder particles and the flattening and smoothing of the same is effected with the aid of a current of air or other gas, preferably an indifferent gas, which is blown continuallv through the machine with a certain suitable strength or force, the current entering the machine on the same side where the metal powder to be treated is introduced, and leaving it at the opposite end, the strength or force of the current being such that it will carry away the finished particles from the flattening and smoothing device of the machine into a separat ng device in which the particles are subdivided and collected,

can be produced and at the same time these as will be found more fully described hereinafter.

A flattening device designed according to this invention is a longitudinally extending apparatus, preferably in the shape of a drum. Since, while the flattening operation is going on, the individual particles of the metal powder are continually whirled up, and sincethe thinner foils have a greater floating capacity than the thicker ones, the current of air, or other gas, passing through the apparatus assists the thinner foils to pass through the apparatus from one end to the other end, and carries those which are thin enough out oft-he apparatus. or'out of the drum respectively. The thinner toils therefore, do not stay or remain as long in the drum as do the other ones which have not been so intensively acted on.by the flattening members or tools. Therefore, at the charging end of the drum where the unflattened particles are introduced, practically no flattened particles or only a few are present, whereas this is the case more and more in the direction toward the other end of the drum. Obviously by; this method an extraordinarily uniform and also economically good spreading of the particles is attained. This eflect is further promoted by the circumstance that the finished particles leave-the drum quickly and on the shortest way, and do not. therefore, remain lon er in the drum than absolutely necessary. If the particles wo ld remain in the drum longer than is requisite they would be acted .on more than i favorable whereby the "drum would be too much clogged and the consumption of power would be increased, Also the workingof the particles by the flattening members would be impeded.-

Another advantage re ulting from the present improved metho is that difiiculties hitherto encountered are overcome. It can occur that particles which have ialreadv been acted on to a certain degree contact with one another and remain in contact so as to form a body of a certain bulk upon which the current of air or other gas rassinq through the drum cannot act in the desired manner.

As the foils float slowly in the drumthe flattening members or tools, viz. steel balls, can knock them effectively to the bottom of the drum and beat and flatten them there.

A long drum for carrying through the flattening operation is useful for this phase of the method, but not so as regards the sifting by a current of air or other gas, the less so, as the space of the drum is filled with the whirled-up powder, and also the steel balls, i. e. the continually falling balls, are therein contained. Therefore, itis preferable to effect the siftin in a separate space or chamber provided outside the drum, there being then used a stronger current by which not only the finished foils are carried out, but also those which have only partly been finished at the time being and are conducted into the separator in which the first-mentioned foils and the other ones are separated from one another. the latter being then returned to the drum in order to be treated again. In this way, also those finished foils which adhere to one ano her are removed from the flattened drum. The use of a strong air or gas current is advantageous for the product.

While. in the grind ng of substances or materials of anvkind in ball mills the at- .ta nment of as fine grains as possible is considered favorable. it is not so with the manufa cture of bronze colors, in hat there must in this case attention be paid o 'the particles retaining their shape as foils and that the area of the o ls is not too small s nce o herw se the light-retracting ca acity wh h gives to the bronze its particular and eculiar character ceases. Too small particles of bronze spo l the wood appearance thereof and make it look black. as experts term it. Removimr these particles later on by sitting is impossibleabecause their s ze or smallness is a readv below t e meshes of the finest sieves hav ng 10000 meshes per square centimeter. B sides. these too small particles have the disagreeable characteristic that they commence to rind down the fine bronze'foils whereby the final product is s illcm'ore, impaired. F nallv. the absolute y necessary smooth and bright surface of the steel balls is t rebv destroved.

With the known grinding procedure in a ba l m ll the mutual grinding down of the individual particles of the respective material is. as is known by evperience, verv important. if not decisive. But when operat ng in the manner in accordance with this inventiomthe ball mill behaves'otherwise: it can then be caused'to work the m tal particles; in such a manner that they are flatten ed and form thin foils. Thus. the ordinary manner of operat on of the ball mill is transformed into a procedure of quite another nature. If, however, this other manner of operation is ever and ever continued, it changes finally automatically in such a way that the resulting product is a poorly looking grey or brown powder. The difliculties are the greater. the finer the bronze is which is to be produced, and it is, therefore, of very great importance to prevent the flattening procedure from being transformed or converted into the ordinary manner of working of a ball mill.

Now, this is, according to the present invcntion, attained by the current of air or other gas passing through the mill being used in quite a distinct manner particularly suited to the purpose in view. While with the known procedure in the working of ball mills with the aid of a current of air stress is placed upon the production of as fine a powder as possible, and the air or gas current mentioned is used merely for carrying that powder out of the mill, without in any way affecting the shape -ot the grain, the air or gas current is employed, according to the present invention, to prevent such a fine powder from being produced and to remove the suitably thin foils flattened by the balls before they are converted into that fine powder. In other wordsz the shape of the toils is affected by the said air or gas current.

Another object of the present invention is to increase the output by the carrying out of the flattening procedure in stages, i. e. in several phases or steps, in that the particles of the bronze are worked. in the first stage or stages, with tools capable of subjecting them to powerful blows; these tools may be larger balls, or the ordinary balls may be dropped from a greater height. In this way, the particles are flattened preliminarily, and thereafter they are further treated with tools having a less pronounced efiect. This can be done practically. for instance, in this way, that two flattening drums are used, the balls enclosed in the one drum being larger than the balls enclosed in the other drum, and the particles that have been treated in the first drum being then conducted into the second drum and being therein treated until thev are finished.

This manner of carrying out the method has the advantage (when a wind-operated sifter is provided outside the drums) to return those particles which are to be treated again exclusively to that drum in which the smaller balls are active or in which the height of fall of the balls is less. Returning said particles to the other drum would prove hurtful because ,in that case particles-which have alreadv been worked intensively would be worked in this manner a second time which would be too much. When, however, operating in'the manner stated. the further advantage is attained that in the second drum' cont-inuallv a comparatively uniform powder mixture is contained.

Furthermore, by arranging the sifting or drums, a considerably shorter drum can'be used, because in that case there does not exist the necessity of flattening all the particles completely within the rum so that they are finished when they leave the drum. Those not yet finished are returned from the sitter or separator to the drum.

The reduced length of the drum not only results saving of material, in connection with certain constructional advantages, but

has,'in addition thereto, the further-advam.

tage that the ainount of 'the pulverulent material necessary to fill the drum so as to insure the desired eflect can be correspondingly smaller. Cleaning the machine is now far simpler than heretofore.

The improved method can be carried out, for instance, with the aid of a machine as shown diagrammatically and by wav of example on the accompanying drawings on which the main parts are shown in Figure 1 partly in vertical lon itudinal section and partly ins de-view; Figure 2 is a transverse section through the second drum (12) along line A--B in Fig. 1.

The material to be treated is contained in a receptacle 1 from which it is conveyed into the first flattening drum 4 through a pipe 3 by means of a convevingsc'rew 2. In the drum 4 are enclosed steel balls 5, and at the ends of the drum are sieves 6 and 7 which let the bronze powder pass. but retain the steel balls. The bronze which has been treated in the drum by the balls leaves the drum through the balls 15 are retained in the druni bysieves 13 and 14. 9

Both drums are supported ongrollsupon which they can be, and are, rotated. I have 'abstained from showing also the means for this purpose. as-they do not form part of the invention. It is obvious that any suitable means can be made use of for rotating said drums.

The current of air or gas which is to pass through the drum 12 is produced by means of afan 16 which drives the respective fluid througha tube 17 into the tube 10. The current carries along in-the drum the floating particles, that is to say. those which can pass through the meshes of the sieve 14. The mixture of the fluid and the particles of the bronze powder. passes through the tube 18 into the upper chamber 19 of the sifting or separating device 20 which consists of an oblique casing in which are arranged superposed oblique plates 21 forming between them passa cs 23 which communicate 'at their lower en s with an ante-chamber 24 communieating in turn with the upper chamber 19. The bronze powder falls down ,from this chamber upon the uppermost plate 21 and from the latter down into 'the chamber 24 or,

more precisely, down uponthoend of the next a 7 plate 21, and so on. -The air or gas current entering the chamber 19 through the tube 18 and flowing from it into the chamber 24 is here subdivided into a plurality of smaller currents 23 flowing upwardly through between the plates 21, these-currents carrying with it the finished particles, or the finished bronze powder respectively, which is now conveyed by said currents first into a collecting space 25 of the casing 20 and then further into acollecting vessel, a so-called cyclone separator, 26 from which finally it falls down into a .conveying receptacle 27 'of any suitable construction.

The individual small air or gas currents pass through the pulverulent bronze while it drops from one of the plates 21 down to the next, and so on,

until the remaining particles have arrived upon the oblique bottom of the casing 20. I

wish it to be understood that instead of the cyclone separator 26 another, equivalent apparatus may be used for separating the bronze powder and the conveying fluid from one another.

The separating apparatus 26 is connected with the fan 16 by mean'sof a tube 28. There 1s, thus, established a circuit composed of the The particles which are not carried away by the said individual small air or gas currents, in that they are not yet in a finished state, pass through 'the branch 29 back into members 16, 17, 10, 12, 18, 19, 24, 25, 26 and the drum 12 in: order to be treated asecond time.

there may be employed a corresponding number of collecting ves els 27.

Finally, instead of the separating device 20/21 any other, equivalent device may be used; or a sifting device with sieves may be used in connection with said device 20/21, or its equivalent.

I claim:

1. The method As the circuit mentioned is completely closed it can be filled with an indifferent gas.

of producing metallic i powders foruse as bronze colors comprising flattening the metal particles by subjecting them to the action of smooth steel balls m a ball-mill, thereby converting the particles into small thin foils, continually supplying fresh amounts of metal particles to said ballmill at one end, thereof and withdrawing the treated particles at the other end, passing a fluid current through said mill of "such a strength as to carry ofi both finished and unfinished particles, separating them outside said ball-mill and returning the unfinished particles thereto.

' 2. lhe method of producing metallic powders for use as bronze colors, comprising flattening the metal particles in two stages by subjecting them in each stage to the action of steel balls in a ball-mill so as to produce flattened particles in the shapeof small thin foils, the action of the steel balls in the first stage being stronger than in the second stage, continually supplying fresh amounts of metal particles to be treated to the first ball-mill at one end thereof and withdrawing the treated particles at the other end, conveying said particles to the second ball-mill, passing a fluid current through said second ball-mill of such a strength as to carry off both finished and unfinished particle s, separating the same outside said last named ball-mill, and returning the unfinished particles to said ball-mill.

3. The method of producing -metalli'c powders for use as bronze colors, comprising flattening the metal particles in' two stages by subjecting them in each stage to the action ofsmooth steel balls in a ball-mill so as to produce flattened particles in the shape'of small thin foils, the flattening action in the first ball-mill being stronger than in the second ball'mill, continually supplying fresh metal particles to the first ball-mill, withdrawing the treated articles from the second ballmill by a fluid current of such a strength as to carry ofi both the finished and unfinished particles, ball-mill, and returning the unfinished particles to said second ball-mill. I I

In testimony whereof I a'ffix mv signature.

' ERWIN KRAMER.

separating them outside said second 

